Bowling Balls

Bowling balls come in $11$ total sizes, an integer weight between $6$ and $16$ (measured in pounds). In a bowling event, Chef is given a total of $N$ bowling balls, with the $i$-th one being $A_i$ pounds. Some of the bowling balls may have the same weight as the others. Chef can use a bowling ball which is at least $X$ pounds, and at most $Y$ pounds. Find the number of bowling balls Chef can us